1. Field of the Invention
The present invention relates to an air conditioner, and more particularly to prevention of freezing of a heat exchanger in indoor heating operation.
2. Description of the Related Art
As shown in FIG. 4, a conventional air conditioner includes a refrigeration cycle formed by sequentially connecting a compressor 1, a four-way valve 2, an indoor heat exchanger 3, a capillary tube 4 as a pressure reducing device, and an outdoor heat exchanger 5. In cooling operation, the refrigeration cycle forms a refrigerant circulation cycle in which a refrigerant flows from the compressor 1 through the four-way valve 2 to the outdoor heat exchanger 5, then to the capillary tube 4, and returns from the indoor heat exchanger 3 to the compressor 1. In heating operation, the refrigeration cycle forms a refrigerant circulation cycle in which the refrigerant flows from the compressor 1 through the four-way valve 2 to the indoor heat exchanger 3, then to the capillary tube 4, and returns from the outdoor heat exchanger 5 to the compressor 1.
In the refrigeration cycle, the amount of required refrigerant to be circulated is not always the same between cooling and heating capabilities. In order to eliminate such a difference in the amount of refrigerant, a receiver tank 6 is provided between the four-way valve 2 and the indoor heat exchanger 3 as shown in FIG. 4 (see Japanese Patent Laid-Open No. 2001-174092).
The amount of refrigerant in the receiver tank 6, the capillary tube, the volume of air, or the like are adjusted to prevent freezing of a fin or a tube 10 in the heat exchangers 3 and 5 in the cooling operation or the heating operation.